1. Field of the Invention
The present invention is related to a method for alignment of liquid crystal molecules, and more particularly, to a method that uses a hydrogen ion beam for alignment of liquid crystal molecules.
2. Description of Related Art
In convention, ion beam bombardment for alignment of liquid crystal molecules is achieved by using an argon ion beam. The related technologies are already disclosed in many issued patents. For example, U.S. Pat. No. 4,153,529, “Means and method for inducing uniform parallel alignment of liquid crystal material in a liquid crystal cell,” is the first patent about using ion beams for alignment of liquid crystal. This technique is applied mainly for inorganic alignment films, including carbon alignment films. The thickness of the alignment films is about 100-5000 A and the energy of the ion beam is about 1-3 keV.
U.S. Pat. No. 6,020,946, “Dry processing for liquid-crystal displays using low energy ion bombardment,” which belongs to IBM Corporation, also discloses the technique about using ion beams for alignment of liquid crystal. The main difference between this patent and the previous patent, i.e. U.S. Pat. No. 4,153,529, is that the thickness of the alignment films and the energy of the used ion beam are different. The thickness of the alignment films disclosed in this patent is about 10-100 A and the energy of the used ion beam is about 75-200 eV.
U.S. Pat. No. 5,030,322, “Method of forming orientation film of liquid-crystal display device,” issued in 1991 and owned by Sharp Corporation discloses the technique about using ion beams for alignment of liquid crystal. This technique is applied mainly for organic alignment films that are made of polyimide (PI), polyurethane (PU), or polyamide (PA).
U.S. Pat. No. 5,770,826, “Atomic beam alignment of liquid-crystals,” owned by IBM Corporation discloses the application of ion beams on organic alignment films that are substantially made of PI. The energy is limited to a level below 200 eV to mitigate the surface deterioration of the organic alignment films caused by high-energy ion beams.
In U.S. Pat. No. 6,485,614, “Method to stabilize a carbon alignment layer for liquid crystal displays,” IBM Corporation proposed a technique of performing a hydrogen process on the alignment films after the alignment process is performed by using ion beams. This technique is used mainly to passivate dangling bonds.
U.S. Pat. No. 6,665,033, “Method for forming alignment layer by ion beam surface modification,” owned by IBM Corporation also discloses a technique about passivation of dangling bonds. The difference between this patent and U.S. Pat. No. 6,485,614 is that the ion beams can be combined with reactive gases, such as silane, tetrafluoromethane (CF4), nitrogen, oxygen, hydrogen, and fluorine, for in-situ passivation of dangling bonds.
Reference is made to FIG. 1, which is a schematic diagram showing an argon ion beam impacting an alignment layer in accordance with the prior art. It shows a device having a glass substrate 10, a conductive layer 12 formed on the glass substrate 10, and an alignment layer 14 formed on the conductive layer 12. An argon ion beam 16 is used to impact the alignment layer 14 and thus causes chemical and physical destruction 18 on the surface of the alignment layer 14.
In the above-mentioned literatures, argon ion beams are used for alignment process. However, since the argon ion beams have low chemical activity and large particles, serious physical destruction is easy to occur on the surface of the alignment films and deteriorates them. The physical and chemical destruction may act as the active sites for ions trapping and problems of image flicker and image sticking thus happen. In U.S. Pat. No. 6,485,614 proposed by IBM Corporation, an argon ion beam is used to impact an alignment film and then hydrogen atoms are used to passivate dangling bonds. In another patent proposed by IBM Corporation, i.e. U.S. Pat. No. 6,665,033, reactive ions are applied on dangling bonds to form a passivation layer.
Accordingly, as discussed above, the prior art still has some drawbacks that could be improved upon. The present invention aims to resolve the drawbacks of the prior art.